Does swapping stereo fool your eyes?

A cream and purple exhibit table with back board that has the text 'Does swapping stereo fool your eyes?' displayed. A clear plastic head sits on a purple flat disc along with black headphones on the table top.

Your vision works out where things are (the location of something), while your hearing works out when things happen (the timing of something).

How it works

Wear a pair of headphones while you watch and listen to ringing bells around a dummy's head. The headphones let you listen to the ringing bells from the perspective of the dummy's head.

Things to try or ask around the exhibit

  • When you swap the audio over between your ears, work out which bell is ringing while your eyes are open and closed.
  • Does your vision influences where you think the sound is originating?

Background

While vision and hearing tend to wrestle for prime sensory position, a new hypothesis about ventriloquism reveals a more co-operative process used by your brain in combining visual and audio signals.

When you swap the audio in this exhibit, the audio and visual signals about which bell is ringing no longer match, but your vision dominates to work out the location of the ringing bell.

A tiny round structure in your brain (inferior colliculus) may process both audio and visual signals preconsciously before they reach your cortex. This means that visual and auditory information may get combined before the 'thinking part' of your brain can make sense of it. As a result, your brain seems to associate a ventriloquist’s voice with the dummy’s moving mouth before you have a chance to consciously think about it.

Finding the science in your world

The next time you’re watching television, think about whether the soundtrack seems to be coming from the actors on the screen, or from the speakers mounted near the television, then close your eyes.

When you’re watching a lecturer on stage and hearing their voice being broadcast from surrounding speakers, you still believe the voice is coming from the lecturer’s mouth.